Ion mobility sensors and gas chromatograph/ion mobility sensor coupled systems are known. And ion mobility sensor is used to measure or indirectly derive the speed of ionic molecules under an electrical field in air (the mobility of ions in air). Different molecular ions have different mobility. Therefore, one can determine different molecules with this measurement. In the conventionally known GC/IMS coupled systems macro size separation columns and large gas flow rates are used and selectivity of the gas chromatograph and sensitivity of the ion mobility sensor are compromised. To avoid using a large tank of carrier gas, the conventional systems use a recirculation pump and a repetitive sample concentration unit. For a sample with parts per million impurity, ion current calculated current calculation is in the order of femto amperes. In other words, it is impossible to employ a conventional ion mobility sensor in coupling with the had-held gas chromatograph to be useful. The prior art gas chromatograph/ion mobility sensor coupled systems are exemplified by U.S. Pat. No. 4,633,083 issued Dec. 30, 1986; U.S. Pat. No. 5,574,277 issued Nov. 12, 1996, U.S. Pat. No. 5,736,739 issued Apr. 7, 1998; and U.S. Pat. No. 5,811,059 issued Sep. 22, 1998, and International Application WO 99/41601 published Aug. 19, 1999.
The present invention provides a solution to the above-referenced problems of the GC/IMS coupled systems, by employing a detector which can detect both ions and molecules simultaneously, and the IMS of this invention can detect and measure the relative arrival times between various ions and molecules. The IMS of this invention utilizes a pair of glow discharge devices, one as an ionizer and the other as an ion and molecule detector. The glow discharge devices of this invention are constructed similar to the glow discharge device described and claimed an copending application Ser. No. 09/464,668, filed Dec. 15, 1999, entitled “Glow Discharge Detector”, assigned to the same assignee.